Gathering of the Figments

Figment · Posted: Sun Feb 04, 2007 3:27 am Post subject: -ible vs. -able

From: http://owl.english.purdue.edu/handouts/grammar/

Rule
-ible -able
If the root is not a complete word, add -ible.

aud + ible = audible
Examples:

visible
horrible
terrible
possible
edible
eligible
incredible
permissible
If the root is a complete word, add -able.

accept + able = acceptable
Examples:

fashionable
laughable
suitable
dependable
comfortable
If the root is a complete word ending in -e, drop the final -e and add -able.

excuse - e+ able = excusable
Examples:

advisable
desirable
valuable
debatable

Some exceptions:

contemptible
digestible
flexible
responsible
irritable
inevitable
You can try some exercises for spelling -ible and -able correctly.

http://owl.english.purdue.edu/handouts/grammar/g_spelibleEX1.html
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